Disease Control Attributes of Oxathiapiprolin Fungicides for Management of Cucurbit Downy Mildew

≤ 0.049). Disease severity on the outer half leaf portion protected from spray deposition during fungicide application was lower for oxathiapiprolin-based fungicides (1.6 to 6.6%) than observed for fluopicolide + propamocarb (10.9 to 23.7%), mefenoxam + mancozeb (40.3 to 51.4%), and the nontreated controls (83.3 to 84.9%), which indicates significant acropetal movement within the leaf. Postinfection applications of oxathiapiprolin-based formulations had the greatest effect on lesion growth and sporangia production compared with the other fungicides in the experiment. When applied preventively to rapidly growing plants in a greenhouse, oxathiapiprolin-based fungicides consistently protected new growth that was not present at the time of application, with the OD formulation reducing disease severity by >75% relative to nontreated plants. The practical implications of these observations are discussed.